btnSend_Click send user to new page

I have a contact page that sends me an email and I am trying to work out how to have it send the user to a ?thank you? page after it completes the send mail action. Is there  just a line or two of code I can add to the ?btnSend_Click? after the smtpClient.Send() runs?
 Also how can I concontate the text from two textboxs into the body of my email.
This works just fine, txtBody being the textbox where the user enters their message ?
mailMessage.Body = txtBody.Text.Trim();
 But when I try doing something like where txtEmail and txtBody are two textboxes that I want to form the body of the email?
mailMessage.Body = txtEmail + txtBody.Text.Trim();
it kills my smtp.Client.Send() function. It stops working.  
 I guessing I just don?t have it constructed correctly. Can anyone point me in the right direction?
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